We are studying the physiological mechanisms that could mediate the precision with which feeding can maintain caloric intake constant in Rhesus monkeys. We have demonstrated that gastric emptying is a controlled phenomenon regulating, within certain ranges of volume and concentration of ingested calories, the flow of calories to the small bowel and portal circulation. We are correlating this phenomenon with the feeding to discern its importance in the behavior and as well observing changes in both variables provoked by brain lesions (ventromedial and lateral hypothalamus), by vagotomy, and by metabolic events, (plasma insulin changes, circulating blood sugar and free fatty acids.) Our overall objectives are to document the relationships between the control of feeding and the neural, metabolic and gastrointestinal mechanisms known tied to it.